Ammonia is applied to soils as a nitrogen fertilizer. The ammonia used for these purposes is usually stored in compressed form as a liquid at ambient temperature. Because of its vapor pressure, liquid ammonia at ambient storage is generally under a pressure of about 80 to about 200 psig. Conventionally, ammonia is applied to soils by injection through a series of socalled knives, which are pulled through the soil at a depth of about 6 to 15 inches. The ammonia is supplied from a pressure tank through a metering valve and discharged behind the tip of each knife. The pressure of the ammonia is released partly at the metering valve and partly at the knife end. Since the expansion of compressed ammonia occurs instantaneously, an intimate mixture of vapor and droplets form at the point of expansion.
Ammonia in the form of an aqueous solution has been applied to anerobically fermentable plant material for silage production to provide feed for ruminant animals, the applied ammonia being converted to nitrogen compounds providing nonprotein nitrogen (NPN) which is consumable by ruminant animals, as taught, for example, in U.S. Pat. No. 3,753,723, incorporated herein by reference. In field applications such as in soil fertilization and trench silage production, this method has serious disadvantages due to the necessity of carrying a separate water supply along with the ammonia and other field equipment. A more economical and simpler method of application of ammonia to soils and silage is described in U.S. Pat. No. 3,978,681 and in U.S. Pat. No. 4,069,029, each incorporated herein by reference, which disclose methods in which the pressure of the compressed, liquid ammonia is released prior to application in an expansion chamber which separates the gas from the liquid. Both phases are then applied to the soil or silage separately, thereby allowing a more uniform flow and a safer non-pressure application. An additional advantage of these methods is that they permit, in the case of soils, the application of ammonia with a conventional disc harrow or cultivator instead of a special knife applicator. Since the cold liquid and gaseous ammonia produced by these processes do not flash or sputter at substantially atmospheric pressure as easily as when pressurized liquid ammonia is applied to the soil directly in the prior art process, the cold ammonia can be applied to the top of the soil or at much shallower depths in combination with the field cultivator so that the cold ammonia thus applied is covered immediately by the soil turned over by the field cultivator. Thus a separate trip over the field to apply ammonia is eliminated. This results in fuel, labor, and machinery wear savings. Also eliminated is the need for knife maintenance and replacement costs.
The shortcoming of the apparatus and process for applying cold liquid ammonia at substantially ambient or atmospheric pressure is in the distribution of the initial stream of cold liquid ammonia leaving the pressure release chamber to a plurality of spaced streams for application to the soil or other use. Since the division of this initial liquid stream must be accomplished substantially in the absence of pressure the distribution problem is an especially difficult one. Gravity flow of this initial liquid stream to a notched weir or over an inverted cone were tried unsuccessfully. If one tries to operate the equipment to apply ammonia to the soil on a field cultivator on somewhat hilly land which results in tilting the equipment then erratic, non-uniform distribution usually results. This lack of control of ammonia distribution is a particularly severe problem when it becomes necessary to vary the ammonia flow rate by a factor of between about 1 to 15 which is a common requirement for application of ammonia to the soil using the different sizes of field cultivators available. The term "field cultivator" is used herein to mean a plow, disc, cultivator, harrow or other suitable soil tillage equipment capable of turning the soil sufficiently to allow ammonia applied to the soil in front of the equipment to be covered to prevent significant immediate loss of ammonia.